This invention relates to an intraocular lens (IOL) and more particularly to an IOL having fixation members which achieve maximum contact with the capsular bag when implanted.
IOL's are a well known type of implant used to replace the natural lens of an eye when the natural lens becomes sufficiently impaired as a result of trauma or disease. An IOL typically includes an optic and at least one fixation member attached to the optic. The fixation member functions to position the optic in correct optical alignment within the eye.
The optic may be constructed of a hard biocompatible polymer, such as polymethylmethacrylate (PMMA). Alternatively, the optic can be constructed from a relatively flexible or deformable material, such as silicone based or acrylic based polymers. When so constructed, the optic can be folded or flexed into a relatively small cross sectional configuration to permit it to be inserted through a relatively small incision into the eye to reduce the trauma and likelihood of infection from the surgery.
Each of the fixation members may be an elongated, resilient strand-like member. Fixation members are constructed of resilient material such as PMMA or polypropylene. In some IOL's, the fixation members are integrally formed with the optic. In other types of IOL's, the fixation members are formed apart from the optic and then attached to the optic.
An IOL can be implanted at different locations within the eye. One common location for implanting of an IOL is the capsular bag.
When an IOL is implanted in the capsular bag, it is desired to achieve a long length of contact between the fixation members and the bag. This reduces unit loading on the bag along the length of the fixation members. When the length of contact between the fixation members and the bag is too short, various problems may result, such as forcing of the bag out of its natural circular shape into an oval shape, stressing the zonules (fibers that attach the bag to the ciliary sulcus), possible irritation or rupture of the zonules and/or the creation of folds in the bag that can disrupt visual acuity and encourage posterior capsule opacification, i.e. the formation of a secondary cataract.
Dusek U.S. Pat. No. 4,863,464 shows an IOL which apparently achieves relatively long contact between the fixation members and the interior structure of the eye. However, these fixation members extend beyond the width of the optic thereby providing an insertion envelope that is larger than the optic, and this is not desirable. Southard U.S. Pat. No. 5,197,981 discloses an IOL which is said to contact more fully and to tension more evenly the capsular bag. However, this construction is made more complex by the requirement that the fixation members have varying cross sectional areas along their lengths. In addition, the fixation members are not configured in a way that is believed to achieve optimal contact with the capsular bag.